Thermoregulation and Stress Hormone Recovery After Exercise Dehydration: Comparison of Rehydration Methods

Abstract

Context: Athletic trainers recommend and use a multitude of rehydration (REHY) methods with their patients. The REHY modality that most effectively facilitates recovery is unknown. Objective: To compare 5 common REHY methods for thermoregulatory and stress hormone recovery after exercise dehydration (EXDE) in trained participants. Design: Randomized, cross-over, controlled study. Patients or Other Participants: Twelve physically active, non–heat-acclimatized men (age = 23 ± 4 years, height = 180 ± 6 cm, mass = 81.3 ± 3.7 kg, V̇o2max = 56.9 ± 4.4 mL·min−1·kg−1, body fat = 7.9% ± 3%) participated. Intervention(s): Participants completed 20-hour fluid restriction and 2-hour EXDE; they then received no fluid (NF) or REHY (half-normal saline) via ad libitum (AL), oral (OR), intravenous (IV), or combination IV and OR (IV + OR) routes for 30 minutes; and then were observed for another 30 minutes. Main Outcome Measure(s): Body mass, rectal temperature, 4-site mean weighted skin temperature, plasma stress hormone concentrations, and environmental symptoms questionnaire (ESQ) score. Results: Participants were hypohydrated (body mass −4.23% ± 0.22%) post-EXDE. Rectal temperature for the NF group was significantly greater than for the IV group (P = .023) at 30 minutes after beginning REHY (REHY30) and greater than OR, IV, and IV + OR (P ≤ .009) but not AL (P = .068) at REHY60. Mean weighted skin temperature during AL was less than during IV + OR at REHY5 (P = .019). The AL participants demonstrated increased plasma cortisol concentrations compared with IV + OR, independent of time (P = .015). No differences existed between catecholamine concentrations across treatments (P > .05). The ESQ score was increased at REHY60 for NF, AL, OR, and IV (P < .05) but not for IV + OR (P = .217). The NF ESQ score was greater than that of IV + OR at REHY60 (P = .012). Conclusions: Combination IV + OR REHY reduced body temperature to a greater degree than OR and AL REHY when compared with NF. Future studies addressing clinical implications are needed.